migrate to maven for building project

- add basic maven configuration including all dependencies
- restructure commonsware libraries in libs directory so that maven can
  find them
- fix ambiguous call to SSLSocketFactory constructor
- (sadly) drop back to API level 16.  This is because ActionBarSherlock
  is built against the android artifacts in maven central, which only go
  up to 16.  Trying to use our own artifacts at 17 causes problems when
  dexing.  We're not actually using anything in 17 right now, so it's
  not that big of a deal.
- add readme file with build instructions